Method of applying powdered metal briquettes to curved metallic surfaces



Oct. 12, 1948. s. K. WELLMAN METHOD OF APPLYING POWDERED METAL BRI QUETSTO CURVED METALLIC SURFACES 1943 2 Sheets-Sheet 1 iginal Filed Sept. 13,

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INVENTOR.

Oct. 12, 1948.

s. K. WELLMAN 2,451,264 METHOD OF APPLY POWDE METAL BRIQUETS TO CURVEETALLI URFACES Original Filed Sept. 13, 1943 2 Sheets-Sheet 2 y 725 FinZ4 04 .2/ /////2% l- 3 I 2 v INVENTOR.

51. u llman m dz l l-m w Patented Oct. 12,1948

OFFICE METHOD OF APPLYING POWDERED METAL- BRIQUETTES TO CURVED METALLICSUR- FACES Samuel K. Wellman, Cleveland Heights, Ohio, assignor to TheS. K. Wellman Company, Cleveland, Ohio, a corporation of Ohio Originalapplication September 13, 1943, Serial Divided and this applicationMarch 14, 1945, Serial No. 582,756

2 Claims. (Cl. 29-1523) This invention relates to a method of applyingpowdered metal briquets to curved surfaces, and more especially forapplying brake liners to brake drums for vehicles and the like.

One of the objects of the invention is the provision of a new andimproved method of applying brake liners to brake drums in such mannerthat the material of the liner becomes intimately bonded to the materialof the drum.

Another object of the invention is the provision of a novel method ofsimultaneously applying a plurality of brake liners of powdered metal toa brake drum with a minimum of time and effort.

A still further object of the invention is the provision of a new andimproved method of applying brake liners made from powdered metal tobrake drums in an emcient, economical and expeditious manner.

Other and further objects and advantages of the invention will appearfrom the following description, taken in connection with theaccompanying drawings in which Fig. l is a vertical section of a heattreating furnace, showing suitable brazing apparatus in position thereinfor carrying out the method of my invention;

Fig. 2 is a vertical section of the brazing apparatus, on the line 22 ofFig. 3.;

Fig. 3 is a section on the line 3-3 of Fig. 2; Fig. 4 is a verticalsection of a portion of an 2 elevated temperature below the meltingpoint of the metal powder. This compressed and sintered powdered metalmay be composed of a mixture of 'metallic and non-metallic ingredients,so that plating may have a thickness of about .0001,

inverted brake drum, showing the brake liners secured to the drumflange, and with a temporary reinforcing member in position thereon; and

Fig. 5 is' a view similar to Fig. 4, but showing the temporaryreinforcing member removed.

It is well known that brake drums become scored and worn in use,resulting in uneven braking and rapid wear of the brake lining. The arthasgenerally used a pressed steel brake drum or a cast iron brake drum,or combinations of the two. lacks wear resistance. Cast iron has thenecessary wear resistance but lacks strength. Therefore. it is common toprovide a steel drum with a wearing surface layer of cast iron.

The present invention proposes to-substitute a layer of sinteredpowdered metal for the cast iron lining in a pressed steel brake drum,in order to obtain better heat dissipation and the desired coefllcientoffriction, as may be predetermined.

Metal powder, if subjected to pressure to compactrit into the desiredshape (usually about eleven tonsvper square inch is used), will sintertogether and unite to form a porous metallic article of considerablestrength if heated to an Steel has the requisite strength but,

and may serve primarily as a protective medium rather than as a brazingmedium in that it prevents reoxldation of the steel after it has beencarefully cleaned. If metal powder is pressed against the preparedsurface of the brake drum with suflicient pressure, and heated to asintering temperature while under pressure, it will bond thereto.

The sequence of operations may, therefore, be described as follows:

1. Press metal powder under a pressure of 11 tons per square inch toobtain a compact or briquet, which, for convenience" of description,will hereinafter be termed a briquet.

2. Clean the surface of the brake drum and metallize this surface in anysuitable manner, as

by electroplating the same.

3. Place the briquet on the clean surface and press it thereagainstunder pressure, say, around 250 pounds per square inch.

4. Heat the drum and briquet while under pressure to sinteringtemperature, which will vary for different materials but which will besomewhere around 1600" F. It isheated and pressed until the metal powdersinters together and bonds to the steel.

As an alternative, the metal powder briquet may be sintered prior tostep 3, in which case the final heating step merely serves to bond thealready sintered briquet to the steel drum.

The above sequence of operations constitutes the usual operatingprocedure in producing certa'in types of bimetallic metal, and is aconventional method in securing any powdered metal to a steel backing.In the ease of annular surfaces, it is exceedingly diflicult to keep thebriquet pressed against the steel backing during the sin-.- tering andbonding operation, and the present invention is designed to accomplishthis object.

For simplicity of disclosure the application of powdered metal briquetsto brake drums has been selected to illustrate one embodiment of theinvention, but it is understood that this is by way of example only; andthat the invention contemplates the application of powdered briquets tocurved surfaces wherever necessary or desirable.

Referring now to the drawing, the reference character l designates,generally, a heat treating furnace within which is mounted the brazingapparatus II. The heat treating furnace l0 may be of any desirableconstruction, that shown being substantially the same as that disclosedin my Patent No. 2,258,431, of October 7, 1941, and which comprises abase portion l2, an intermediate or furnace covered structure l3 havingtop and side walls of refractory material, as is usual in suchconstructions. The intermediate portion is provided with electricalheating elements I4, and an air sealed member l5 extends over thebrazing apparatus H, with its side walls extending down into looseinsulating material l6. Means for applying air pressure to the brazingapparatus is shown at H.

Since the details of the heat treating furnace constitute no part of thepresent invention, it is not thought necessary to further illustrate ordescribe the same.

The brazing apparatus H, which is positioned within the furnace l0,comprises a plurality of separate superposed sections or units l8, I9,20 and 2|, only four being shown; but the apparatus may be contracted orextended by removing one or more of the sections or by adding additionalsections, as occasion may require, or for accommodating various sizes ofheat treating furnaces. This is considered an important feature of theinvention.

These sections are preferably, though not necessarily, duplicates ofeach other, except for the bottom or foundation member 2| which may beregarded as having its lower portion removed. Its upper portion may besubstantially like the upper portion of the other sections. Each ofthese sections is provided on its upper surface with an annular steppedportion conforming to the brake drum, as shown in Fig. 2. In otherwords, each section is cylindrical in form and has a lower horizontalportion 22, on which the attaching flange 23 of a brake drum 20 isadapted to rest and be clamped in position by suitable bolts or screws24 extending through the attaching flange 23 into the section. Eachsection is provided with a top horizontal portion 25 above, and offsetradially outwardly from, the horizontal portion 22, on which an offsetportion 26 of the brake drum 20 is adapted to seat. The brake drumflange 21 extends vertically upwardly from the top of the section towhich it is attached.

The lower portion of each section, except the lower one, is providedwith means for positioning the brake liners or briquets on the brakeflange, and for clamping the same in position during the heat treatingoperation. As shown, each of the upper sections is provided with acircular recess 28 extending upwardly from its bottom wall, and intowhich the drum flange 21 extends, as shown more clearly in Fig. 2 of thedrawing. The recess 28 has upwardly converging walls 29 and 3|. Thesewalls are both shown as being inclined to the vertical and convergeupwardly, but the wall opposite the briquet could, of course, be avertical wall since it functions as an abutment wall reacting againstthe wedge on the opposite side of the brake flange. However, since thebrazing apparatus is adapted to be used for creating opposite pressuresagainst the brake drum flange, whether the briquet is secured to theinner or outer surface, it is preferred that both walls of the groove beinclined, as shown in Fig. 2.

With this arrangement the powdered metal briquets may be applied toeither the inner or outer surface of the brake drum flange or to bothsides, or some to one side of the drum flange and some to the other,simultaneously, as may be desired. By means of this arrangement pressureis applied to both sides of the brake flange, and consequently alldanger of distorting the flange is eliminated.

The brake liners 32, or rather what is destined to become the brakeliners, are of powdered metal and conform to the surface of the brakedrum flange 21, to which they are bonded. These liners are first formedby applying pressure to powdered metal to form thesame into the briquets32 (Fig. 4), and these briquets are bent to conform to the curvature ofthe surface of the brake drum flange, whether they be applied to theinner or outer surface thereof.

Suitable means are provided for applying lateral pressure to thebriquets and applying pressure for reinforcing the brake drum flangesfor preventing radial expansion or contraction of the same. As shown, aplurality of outer and inner curved wedge members 33 and 3|,respectively, are employed for this purpose. The wedge members 33 and34, which are segments of circular form, are adapted to be positionedwithin the circular recess 28. The wedge segments or members 33 engagethe outer inclined wall 29 and the outer surface of the brake drumflange or the briquet, as the case may be, and the wedge members 34engage the side of the inclined wall 3| and the flange 21 or thebriquets, as the case may be, as shown in Fig. 2. It will thus be seenthat downward pressure on the section It! will cause the wedge members33 and 34 to exert opposed lateral pressure on the brake flange and thebriquets. The wedge members that contact the briquets should be coatedwith graphite to prevent the briquets from adhering thereto during thesintering operation. The sections of the brazing apparatus may be builtup in like manner, one superposed on the other, to the capacity of theheat treating furnace. Each unit or section has a brakev drum attachedthereto in the same manner as described above.

When the parts have been assembled within the furnace, pressure and heatare app1ied--the heat being substantially that for sintering thebriquets, and the pressure being sumcient to cause them to become bondedto the brake drum flange. Usually a pressure somewhere in theneighborhood of 250 pounds per square inch, with a temperature of around1600 F., will be suflicient, but this will depend upon the nature of thepowdered material constituting the briquets.

The brake liners may be attached to either the inner or outer side ofthe brake drum, as maybe required. As shown in the lower section in Fig.2, the liners 32 are illustrated as being applied to the inner side ofthe brake drum, while the upper one is on the outer side.

The briquets may consist of a single layer of powdered material, asshown at 32 in Fig. 4, or they may be formed by two or more layers, asshown in Fig. 5. Where liners are attached to friction members on brakedrums, the briquets are preferably, though not necessarily, formed of aplurality of layers. In Fig. 5 is shown a briquet of two layers 32' and32. The inner layer 32, or layer in contact with the brake flange. ispreferably of powdered copper because of its heat conductivity, so thatheat generated by the braking operation is conducted away from thefriction surface of the liners and thereby dis sipated.

The brazing apparatus ll may also be used to secure a bimetallic memberto a brake drum by a conventional soldering or brazing operation. Inother words, in the above description the powdered metal is bondeddirectly to the flange of the brake drum. It is also possible to firstsinter and bond the briquet to a thin sheet metal or sheet copperbacking member, and to solder or braze the backing member to the flangeof the drum. Thus, for example, the pure copper layer 32 of Fig. 5 maybe substituted by a solid copper member, the

briquet being pressed and sintered and bonded to the copper backing inthe usual manner. If the copper backing member and the flange of thedrum are heavily plated with copper or tin and then assembled in thebrazing fixture and heated, the sheet copper backing will be welded orbrazed to the flange of the brake drum. However, it is preferred tosecure the powdered metal directly to the flange of the drum.

It is to be observed that the embodiment shown secures powdered metal toa cylindrical surface, but that it is obvious that the surface may beinclined from the vertical in someinstances, such as in cone-shapedbrake drums.

; It is to be noted that the wedges 33 serve to maintain the drum inproper position and to prevent warpage due to heat of the sinteringoperation. If this wedge is omitted the drum distorts badly and is notusable.

The composition of the facing or friction laye may vary for differentuses and installations. The

following mixture for the layers 32* and 32' has been found to givesatisfactory results:

Per cent Copper 73 Lead 14 Tin 7 Graphite 6 The briquet must obviouslyconform to the shape of the flange of the brake drumin which it is to besecured. The only satisfactory manner in which this can be done is toform a flat rectangular briquet and then bend it to a curvaturecorresponding to the flange of the drum. Several such arcuate segmentsare placed end to end to form the complete lining for theflange.

Due to the danger of fracturing the briquets in curving the same,esp-.cially in the thicker briquets that may have been sintered, it hasbeen found that ii a temporary reinforcing member of thin sheet steel 35(Fig. 4) be bonded onto the briquet it may be more easily bent tocurvalinear form without fracturing or rupturing the material, and thismay be done as disclosed in my Patent No. 2,289,311. This member may beremoved or peeled'ofl after the briquet has been bonded tothe brake drumflange 21. This temporary reinforcing member may, if desired, be alsoused in the multi-layer brlquet shown in Fig. 5.

- It will thus be seen that the brazing apparatus comprises apluralityof similar units or sections 6 that are superposed or built into a stackthat may be increased or decreased in height, depending on the capacityof the furnace. It will also be observed that suitable pressure may beapplied to the stack of sections by the use of the inclined walls of thegrooves in cooperation with the wedge members, and that the brake drumsare prevented from becoming distorted by the heat and pressure appliedthereto.

prises forming powdered metal into fiat briquets,

sintering and bonding each briquet to a thin sheet steel reinforcingmember, curving the sintered and reinforced briquets to a shapeconforming to the curvature of the surface of the flange, placing saidbriquets adjacent said surface with each powdered metal briquet disposedbetween the surface of the flange and its steel reinforcing member,applying opposed pressures to opposite sides of said briquets and flangewhile simultaneously heating said drum and briquets to the sinteringtemperature of the latter for bonding'saidbriquets to the surface of theflange and then removing said thin steel reinforcing members from thebriquets.

2. A method of attaching brake liners to the surface of the flange of abrake drum which comprises forming powdered metal into fiat briquetshaving a layer of copper and a layer of a mixture of metallic and non-metallic powders, sintering and bonding each briquet to a thin sheetsteel reinforcing member with the reinforcing member bonded to the layerof a mixture of metallic and non-metallic powders, curving the sinteredand reinforced briquets to a shape conforming to the curvature of thesurface of the flange, placing said briquets adjacent said surface withthe layer of copper disposed against said surface of the flange,applying opposed pressures to opposite sides of said briquets and flangewhile simultaneously heating said drum and briquets to the sinteringtemperature of the latter for bonding said briquets to the surface ofthe flange and then removing said thin steel reinforcing members fromthe briquets. 1

' v SAMUEL K. WELLMAN.

REFERENCES CITED The following references are of record in the flle ofthis patent:.

UNITED STATES PATENTS Number Name Date 1,556,746 Bartholomew Oct. 13,1925 1,768,529 Short June 24, 1930 2,044,924 Timken June 23, 1936 I2,129,125 Geyer Sept! e, 1938 2,178,527 Wellman Oct.- 31, 1939 2,287,952Tormyn June 30, 1942 2,289,311 Wellman July 7, 1942

